Automatic server for machine for running pairs of gears together

ABSTRACT

For a machine for running pairs of gears together, e.g., for lapping or testing one pair at a time, there is provided an incoming magazine, an outgoing magazine, a conveyor device which moves gear pairs toward the front of the incoming magazine; a conveyor device which moves gear pairs toward the back of the outgoing magazine; a transfer device which moves two pairs of gears across the machine at once: taking one pair from the machine&#39;&#39;s work station and another from the front of the incoming magazine and shifting these pairs, respectively, to the front of the outgoing magazine (or to a reject chute) and the machine&#39;&#39;s work station. The gears are oriented in the incoming magazine so they will mesh when mounted at the work station. The server is responsive to tests performed at the work station to reject and replace any damaged or improperly paired gears or any gear pair improperly installed at the work station and to indicate the reaons for rejection on a register which shifts as additional pairs are rejected so the machine operator can quickly discern which gear pair was rejected for which reason. A telescoping cover encloses the work station during the lapping operation to prevent contamination of the transfer mechanism.

[451 Aug. 29, 1972 United States Patent Ellwanger [57] ABSTRACT For a machine for running pairs of gears t for lapping or testing one pair at a time,

[54] AUTOMATIC SERVER FOR MACHINE FOR RUNNING PAIRS OF GEARS ogether, e. g.,

there is provided an incoming magazine, an outgoing magazine, a conveyor device which moves gear pairs toward the front of the incoming magazine; a conveyor device which moves gear pairs toward the back of the outgoing magazine; a transfer device which moves two pairs of gears across the machine at once: taking one pair from the machine's work station and another from the front of the incoming magazine and shifting these respectively, to the front of the outgoing magazine (or to a reject chute) and the machine's work station. The gears are oriented in the incoming m m p m m a a MM R R ww m n 0 cm m w s e menus m mum M Gm i m v s in mm m HM .d r s UH. U .U m

52 us. R, 209/75 [51] im. Cl. 47/02 [58] Field of Search.....51/2l5 R; 209/80, 75; 73/162 they mesh when station. The server is responsive to tests performed at the work station to reject and replace any damaged or improperly paired gears or any gear pair improperly References Cited UNITED STATES PATENTS installed at the work station and to indicate the reaons for rejection on a register which shifts as additional pairs are rejected so the machine operator can quickly 2,965,971 12/1960 Pomernacki..........209/8OUX 3,502,208 3/1970 Muller.....................209/80X discern which gear pair was rejected for which reason. A telescoping cover encloses the work station during Primary Examiner-Othell M. Simpson Attorney-Morton A. Polster the lapping operation to prevent contamination of the transfer mechanism.

25 Claims, 22 Drawing Figures PATENTED I97? 3.686.801

sum 01 ur 16 CHARLES 6. ELLW/INGER INVENTOR.

PATENTED 3.686.801

sum near 16 P AFENTED B 2 3.686.801 sum 120E 16 PAIENTEMuczs nan SHEET 15 0F 16 ((IJUQUJ AUTOMATIC SERVER FOR MACHINE FOR RUNNING PAIRS OF GEARS TOGETHER BACKGROUND OF THE INVENTION Bevel and hypoid gear lapping machines run pairs of gears together in mesh at a work station while a fineabrasive lapping compound is sprayed onto the meshing gear teeth, and the gears are translated relative to one another along three axes to traverse the tooth contact area back and forth along the length of the gear teeth. This is done after heat treatment to refine surface finish and tooth bearing characteristics of the pair in order to ensure quiet running and efficient power transmission once the pair of gears is mounted in a product, e.g., an automotive power train differential. Similar machines, without means for applying lapping compound, are used for testing pairs of gears.

Co-pending U.S. Pat. application Ser. No. 98,512, filed Dec. 16, 1970, discloses a machine for lapping a bevel or hypoid gear mounted on a horizontal spindle in mesh with a corresponding pinion mounted on a vertical spindle. The server disclosed in this application was specially designed to serve such a machine. How ever, with minor modifications which do not result in departure from the principles of the disclosed invention, the server can be used as well with other machines for running pairs of gears together.

Gear pairs normally are inspected for certain defects which make the gears unsuited for lapping. Defects such as gross errors in tooth size may require scrapping a part, while other smaller defects such as nicks and burrs can be remedied, especially if detected before lapping is done. These inspections are customarily done by the operator at the time he loads and starts the lapper. Therefore one problem which must be solved by apparatus for fully automating the lapping process is the provision of means for making such essential inspection and for rejecting unsuitable pairs before the lap cycle commences, such rejection of unsuitable parts preferably being done without shutting down the machine and halting the automatic flow of work through the machine.

Upon completion of the lapping operation, gear pairs are usually handled and stored in pairs as lapped. The reason for such procedure is that it is generally not possible to obtain optimum running qualities by interchanging lapped gears and pinions. Thus, a further problem in automating the lapping operation is to provide means for keeping the gears in pairs upon discharge from the work station.

Lapping involves the use of a wet abrasive compound which contaminates the surrounding parts in the lapping chamber, and this compound will drip from any chamber structure located above the workholders following the lapping operation. Prior art lapping operations require the presence of an operator to wipe workholding chucks following each lapping operation to assure that the work-seating surfaces of the chucks are not contaminated with the abrasive compound. This contamination problem has heretofore been a factor militating against automation of lapping machine loadmg.

An automatic conveyor, loader and transfer apparatus serving gear cutting machinery is depicted in US. Pat. Nos. 3,l69,446 and 3,54l,92l. Preferably the jaws of the transfer mechanisms of the device of the present invention are configured and coact substantially as described in these two patents.

SUMMARY OF THE INVENTION The novel automatic server disclosed herein incorporates all of the necessary facilities for automating work handling in a machine for running pairs of gears together for lapping or testing one pair at a time. In the described embodiment, an incoming magazine is provided for storing and advancing gear pair sequentially to a convenient position relative to a bevel and hypoid gear lapping machine. A means is provided for moving each pair in turn from this position in the incoming magazine to a station from which the set is transferred to a work station.

A transfer device including both loading and unloading jaws, operates across the front of the machine for effecting the transferral of successive pairs into and out of the work station. At the work station and before being lapped, a gear pair is subjected to several preliminary tests, namely, (l) a check for proper seating and clamping by the workholders, (2) a check for oversize or undersize teeth and (3) a nick and burr detection.

If the gear pair fails one of the named tests, it is immediately removed from the work station and transferred to a temporary holding station in the form of a reject turntable." Simultaneously the transfer device moves the next succeeding pair into the work station. The defective pair is automatically moved from the reject turntable into a reject chute and, upon arrival at the reject chute, a monitoring system of the shift register type indicates the reason for the rejection of the set. This system continues to identify in its display means the reason for rejection of each pair held within the reject chute.

If, alternatively, a set passes the preliminary tests and subsequent lapping operations are performed, the lapped pair is then withdrawn from the work holder by the same transfer device and transferred to the same holding station, i.e., the reject turntable. In this case the reject turntable will remain oriented such that on the next succeeding operation of the transfer device, the held lapped pair will be moved and arranged for acceptance by an outgoing magazine. The outgoing magazine operates similarly to the incoming magazine, storing and moving the lapped gears and pinions in pairs.

This automatic loading apparatus further solves the problem of aligning teeth and slots so that the pair will be in meshing relationship at the work station by orienting the pinion and gear, in the proper tooth-toslot relationships, in the incoming magazine. Thus upon reaching the work station the gear and pinion are oriented in their proper tooth-mesh position.

As noted above, the preferred embodiment of the subject server is employed on a lapping machine having a horizontal gear spindle and a vertical pinion spindle, and such a machine preferably includes means for effecting axial movement of the gear spindle head of the machine such as is disclosed in the co-pending application, Ser. No. 98,512 referred to above. Such advance and withdraw motion of the gear head is used in the loading-unloading operation, bringing the workholder respectively into and out of engagement with the gear blank held by the transfer jaws. Therefore, by making use of this particular gear head movement, the preferred form of the invention saves a significant amount of additional loading apparatus mechanism that would otherwise be required to move the gear onto the arbor.

The automatic control of the loading-unloading apparatus is efl'ected by a sequencer of the pneumatic type which is of high reliability and utilizes cams to actuate valves which in turn activate pressure switches. The controller and its cams are arranged such that the sequential motions of the loading-unloading mechanism may be readily modified if desired, thus making the system highly flexible.

In addition, the subject server is provided with a novel lapping chamber which comprises a telescoping cover for enclosing the work station during the lapping operation. This cover prevents contamination of the transfer mechanism by the lapping compound during the lapping operation and, since it is folded to a position below the work station after each lapping operation, excess compound remaining on the cover following lapping cannot drip onto or into the workholding and work-handling devices during loading and unloading operations. This novel cover solves a major part of the contamination problem, and substantially contamination-free operation can be achieved when the subject server is used with machines which provide a final spin-cleaning" of the gear pair after lapping and prior to opening of the cover. In this regard, it might be noted that the recently developed lapping machine referred to above includes such a spin-cleaning cycle in which the gear pair is disengaged, following lapping, and both gears are rotated at high speeds to spin them clean of compound just before the opening of the work station cover.

It will be appreciated that the entire loading arrangement and operation of the subject apparatus is designed to require no operator attendance other than for occasional tending of the incoming and outgoing magazines and the reject chute.

The principles and further advantages of the invention will be further hereinafter discussed with reference to the drawings wherein a preferred embodiment is shown. The specifics illustrated in the drawings are intended to exemplify, rather than limit, aspect of the invention as defined in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a perspective view of a machine for running a pair of gears together in mesh, e.g., for lapping, machine which is equipped with an automatic server constructed in accordance with the principles of the present invention;

FIG. 2 is a schematic perspective view of the automatic server;

FIG. 3 is a schematic development of the cycle drum which controls operation of the automatic server;

FIG. 4 is a front elevation view of the support and mounting of the gear pair transfer device, also showing the pusher arms for moving workpieces from the reject turntable to the unload rest;

FIG. 5 is a side elevation view of a front portion of the transfer device of FIG. 3, showing the device in partial section;

FIG. 6 is a longitudinal sectional view of one of the transfer device jaws for transferring pinions;

FIG. 7 is a longitudinal sectional view of one of the transfer device jaws for transferring gears;

FIG. 8 is a side elevation view of the incoming magazine with parts broken away to expose interior details and certain parts eliminated for purposes of clarity;

FIG. 9 is a partial front end elevation view of the incoming magazine with certain parts omitted for clarity;

FIG. 10 is a top plan view of the incoming magazine shown in FIGS. 8 and 9, also indicating the position of the loading nest in block form;

FIG. 11 is an enlarged partial view (similar to FIG. 9) of a ring gear and pinion at rest in the incoming magazine;

FIGS. 12 and 13 are, respectively, a front elevation view and a top plan view of the loading nest;

FIG. 14 is a top plan view of the reject turntable, unload nest, and a portion of the outgoing magazine;

FIGS. 15 and 16 are enlarged details of the reject turntable in top plan and elevation, respectively;

FIGS. 17 and 18 are, respectively, a side elevation and a partial top plan view of the reject chute mechanism;

FIG. 19 is a partial perspective view of telescoping lapping chamber cover on the front of the machine in its closed position;

FIGS. 20 and 21 are section views of the cover mechanism shown in FIG. 19, illusti'ating the cover in closed and open positions, respectively; and

FIG. 22 is a schematic diagram of the reject system for monitoring pairs of gears which are considered unsuitable for lapping or testing for various reasons.

DETAILED DISCUSSION OF THE PREFERRED EMBODIMENT A machine 10 for running a bevel or hypoid gear in mesh with a corresponding pinion and equipped with an automatic server is depicted in FIG. I from the front and toward the incoming magazine 14 of the automatic server. The automatic server 12 is shown schematically, by itself, from the same aspect in FIG. 2. Generally, the automatic server 12 includes an incoming magazine 14, a load nest 16, a transfer mechanism 18, an unload turntable 20, an unload next 22, an outgoing magazine 24, a reject chute 26, a program control drum 28 and attendant interconnecting elements.

With reference to FIGS. 1 and 2, the movements by the automatic server of typical gear sets through the machine will now be succinctly outlined. Gear pairs, (i.e., sets) are manually placed into the incoming magazine 14. Once for each change of gear pair at the work station W, each gear pair on the incoming magazine is walked forward one step by being raised from A to B then advanced to C and lowered to D. (The walking mechanism resets to A.) For each gear pair, the walking continues until that gear pair has reached position E of the load nest 16. Once there, the gear pair is shifted to position F whereupon the transfer mechanism 18, which is shown in its G position lowers in direction H and its station G, comprising jaw mechanism later to be described, engages the gear set. The transfer mechanism 18 then raises to the I position. Upon reaching the l position, the transfer mechanism l8 shifts in the J direction. This places station G directly over the W or work station position, and places station J (comprising other similar jaw mechanisms later to be described) directly over the M position. Transfer mechanism 18 again lowers in the H direction, and deposits the pinion at position L in the pinion spindle 30. Also while the transfer mechanism 18 is in this position, gear head 32 advances to the K position and receives the gear. While the G station is placing the gear and pinion in their respective work station chucking positions, station J is in the M position, i.e., stations G and J are in the L and M positions their jaw mechanisms respectively disengaging a gear pair at each position. The transfer mechanism then moves upward to the l position and laterally to the G position. If the gear set which has been tested (prior to lapping) was found unacceptable, turntable 20 (position M) rotates in a clockwise direction and disposes the set for movement onto reject chute 26. Here the set is moved in the N direction. Conversely, if the set has been found acceptable and consequently has been lapped, the unload mechanism 22 shifts to the 0 position. From the 0 position the set moves in the P direction. Outgoing magazine 24 walking mechanism advances in the Q direction and raises in the S direction thus picking up the gear set from the unload nest. While in the S position, the outgoing magazine 24 moves the set a step in the R direction, then lowers in the T direction, placing the set in the first of a plurality of compartments in the outgoing magazine, later to be described.

Repetitive operations of the automatic server (as well as certain operations of the machine which are not pertinent to the present discussion) are controlled by the program control drum 28 indicated in FIG. 1 and shown developed schematically in FIG. 3, wherein the various cams stacked to constitute the drum are listed along the vertical scale and the various steps in operation of the automatic server which take place as the program control drum rotates are listed along the horizontal scale. Thus, the curves in FIG. 3 represent the conditions of the respective switching means operated by the cams of the drum as the drum rotates. The control drum is driven in a stepwise manner by a motor actuated by a pressure switch responsive to air pressure indications of the position of the various machine elements. Such control drum systems are known, and one such prior art system is disclosed in detail in U.S. Pat. No. 3,521,524 assigned to the as signee hereof. In the preferred embodiment disclosed herein, the drum cams actuate air pilot valves which remotely control hydraulic valves. Other, equivalent switching means could be used.

The transfer device 18, which is visible through the open doors at the work station W in FIG. 1 is also shown in FIGS. 4-7. Referring first to FIG. 4, there is shown a rail 34 which extends transversely of the machine 10 adjacent the work station. The ends of the rail 34 are fixed in frame extensions 36 of the machine 10. The transfer device includes a bracket 21 slidably received about the rail 34. For moving the transfer device back and forth along the rail 34 there is provided a pressurizable, double acting piston and cylinder arrangement 31 which has one end connected to the bracket 21 and the other end to a frame extension of the machine 10. The bracket 2] includes two transversely spaced, vertically extending sleeves which respectively slidingly receive intermediate portions of shafts 33. The lower ends of the latter are threadably secured at 35 in upwardly open sockets in a carriage 27, providing for slidable vertical displacement of the carriage with respect to the bracket. The displacement is effected by means of a double acting piston and cylinder arrangement 29 which is vertically oriented, the cylinder being fixedly mounted to the bracket 21 and the piston having its lower end secured to carriage 27. The carriage is shown at its uppermost extreme in FIGS. 4 and 5. When the carriage is moved downwardly by pressurization of the double acting piston and cylinder arrangement 29 in a first sense, the shafts 33 act as guides. The jaw mechanisms for grasping two sets of gears are mounted on the back of the carriage 27. Accordingly, they are not visible in FIG. 4, although the gear sets, G and P at the left and G and P at the right, show in this FIG.

However in FIG. 5, one of the pinion jaw mechanisms is depicted at 39 and one of the gear jaw mechanisms is depicted at 40. These mechanisms are respectively shown in more detail in FIGS. 6 and 7. The pinion jaw mechanism 39 and the gear jaw mechanism 40 of each transfer head are rigidly fixed on mounting pads 23 and 25, which are part of the movable carriage 27. Accordingly, pads 23 and 25 move in a downward or upward direction with the carriage 27. When the carriage 27 is at its lowermost position, two of four events may occur. Two are discussed here and two are discussed later.

I. The pinion P is in the pinion spindle 30 and chucked (or dechucked depending on the sequence) and the pinion jaws release the pinion.

2. The gear head 32 advances and its arbor engages and firmly chucks the gear G. The advance of the gear head is controlled by a piston and dashpot arrangement (not shown). The gear head is brought forward to a limit position such as to insure firm seating of the back face of the gear on the workholder. Thereafter, the gear G is firmly chucked in the gear head arbor, the gear head jaws release and the gear and pinion jaw mechanisms 39 and 40 are moved upwards.

When carriage 27 is in its uppermost position, the bracket 21 is moved from right to left or left to right (FIG. 4 orientation) depending on the sequence.

Bracket 21 is supported from rotation about the rail 34 by bearing 41 which slidingly receive a depending flange 42 of the frame extension 36.

The structure and operation of the pinion jaw mechanism 39 can be seen most easily from FIG. 6.

As fluid pressure is introduced into chamfer 63, the piston 58 is caused to move in an upward direction, thereby compressing spring 60. (The piston is shown in uppermost position, i.e., a pinion is clamped in the pinion jaw mechanism jaws.) Upon upward movement of piston 58, the extensions 56 which is pin connected to piston 58 also moves upward. Attached to this extension are two dowel pins 64 which act as drives for jaw member 46. Jaw members 46 have attached to them two inserts 48 which are fixed for adjustment to members 46 and may be changed when the machine 10 is being readjusted to process different size pinions. 

1. For a machine for running together a pair of bevel or hypoid gears for lapping, testing or the like, an automatic server comprising: first conveyor means for receiving and forwarding workpieces to be installed at a work station of said machine; second conveyor means for accepting and tending gears in pairs as they have been removed from the work station; transfer means for moving the workpieces through the work station between the first and second conveyor means and for installing and removing a pair of workpieces in and from respective workholders at said work station; sensing means for sensing, subsequent to operation of said installing means, at least one of the following conditions: a. improper seating and gripping of one of said workpieces by the workholders, or b. improper axial position of one of said two workpieces when said workpieces are in tight meshing engagement at said work station, or c. improper vibration occurring when said two workpieces are in rolling engagement.
 2. The automatic server of claim 1 further comprising program control means automatically, repeatingly interspersing operation of said first conveyor means, said transfer means and said second conveyor means to serially install each gear pair forwarded by the first conveyor means at the work station then remove that gear pair and deposit that gear pair with the second conveyor means.
 3. The automatic server of claim 1 wherein said transfer means includes two, transversely spaced heads, each structured to grasp and let loose a gear pair, said two heads being so spaced relative to the first and second conveyor means that at one disposition of the transfer means, one head is located to accept a gear pair from the first conveyor means and the other head is disposed adjacent the work station for removing a gear pair from the work station, and so that, at another disposition of the transfer means transversely spaced from the first disposition, said other head is disposed to deposit a gear pair removed from the work station upon the second conveyor means, and said one head is located adjacent the work station for installing a gear pair which has been brought from the first conveyor means by said one head.
 4. The automatic server of claim 2 wherein said sensing means is operatively connected to said program control means for initiating operation of the transfer device to remove a gear pair from the work station and simultaneously replace that gear pair with a succeeding gear pair from the first conveyor means and deposit the removed gear pair upon the second conveyor means.
 5. The automatic server of claim 4 wherein the second conveyor includes: an outgoing magazine for accepting gear pairs which have been worked upon at the work station; a reject chute for accepting gear pairs which have been removed from the work station due to sensation of at least one of said conditions (a) through (c); turntable means normally disposed to accept gear pairs from the transfer device and feed them toward the outgoing magazine unless the gear pair deposited upon the turntable by the transfer device is removed from the work station due to the sensation of at least one of the conditions (a) through (c), in which case the turntable is operable to become temporarily disposed to feed that gear pair to the reject chute; and said turntable being operatively connected to said program control means for automatic control of the disposition thereof.
 6. The automatic server of claim 5 further including display register means for serially, visually indicating the reason(s) for rejection of each gear pair forwarded to the reject chute.
 7. The automatic server of claim 6 wherein said display register means includes shift means operable upon at least one of deposit of another gear pair in the reject chute and removal of a gear pair from the reject chute to displace, add and delete visual indications of reasons for rejection of the gear pairs remaining in the reject chute.
 8. The automatic server of claim 5 wherein the second conveyor further includes an unload nest haviNg means for accepting a gear pair from the turntable.
 9. The automatic server of claim 8 wherein the transfer means includes adjustable pusher arms for moving a gear pair from said turntable into said unload nest.
 10. The automatic server of claim 9 wherein said unload next has movable means cooperating with said adjustable pusher arms for disposing the gear pair for acceptance by the outgoing magazine.
 11. The automatic server of claim 10 wherein the outgoing magazine includes walking beam means intermittently operable to advance gear pairs accepted thereby one step therein; said walking beam means having a portion disposed to walk pairs of gears from the unload nest into the outgoing magazine.
 12. The automatic server of claim 11 wherein the relative disposition of the gears of each gear pair installed at the work station differs from the relative disposition of the gears of each gear pair in the outgoing magazine and said unload nest movable means and said pusher arm adjustable means cooperate to adjust the relative dispositions of each gear pair to that relative disposition in the outgoing magazine.
 13. The automatic server of claim 2 wherein the second conveyor includes: an outgoing magazine for accepting gear pairs which have been worked upon at the work station; and an unload next interposed between the transfer device and the outgoing magazine for accepting gear pairs from the former and for cooperating with adjustable pusher arms operable as a part of said transfer device to dispose said gear pairs for acceptance by said outgoing magazine; and said outgoing magazine includes walking beam means intermittently operable to advance gear pairs accepted thereby by one step therein; said walking beam means having a portion disposed to walk pairs of gears from the unload nest into the outgoing magazine.
 14. The automatic server of claim 13 wherein the relative disposition of the gears of each gear pair installed at the work station differs from the relative disposition of the gears of each gear pair in the outgoing magazine and said unload nest includes movable means cooperating with said pusher arms for adjusting the relative dispositions of each gear pair received thereby for transferral to the outgoing magazine.
 15. The automatic server of claim 2 wherein the first conveyor includes: an incoming magazine; a load nest interposed between the incoming magazine and the transfer device for accepting gear pairs from the former and disposing them for acceptance by the latter; the incoming magazine including walking beam means intermittently operable to advance gear pairs accepted thereby by one step therein; said walking beam means having a portion disposed to walk pairs of gears from the incoming magazine into the load nest.
 16. The automatic server of claim 15 wherein the relative disposition of the gears of each gear pair installed at the work station differs from the relative disposition of the gears of each gear pair in the incoming magazine and said load nest includes means for adjusting the relative dispositions of each gear pair received thereby while transferring that gear pair from the incoming magazine to the transfer device.
 17. The automatic loader of claim 1 wherein the transfer device is configured to grasp a pinion disposed with its longitudinal axis vertical and a bevel or hypoid gear with its longitudinal axis horizontal.
 18. The automatic server of claim 1 wherein said first conveyor means includes means for sensing relative angular positioning of each gear with respect to its teeth so that when pairs of gears are installed at the work station and brought together they will dependably mesh rather than clash.
 19. The automatic server of claim 2 further comprising cover means movable to and from a position enclosing the workholders at said work station and responsive to said program control means, said cover means moving to said enclosed position only when the workpieces are installed in said workholders.
 20. The automatic server of claim 19 wherein said cover means comprises a plurality of telescoping members each of which moves inside the next respective one thereof.
 21. The automatic server of claim 20 wherein said telescoping members have overlapping edge means which interconnect when said cover means is moved to said work station enclosing station.
 22. For a machine for running gear pairs together in mesh at a work station for lapping or testing, each gear pair consisting of a bevel or hypoid gear and a corresponding pinion, the bevel or hypoid gear of the pair being mounted for rotation on a horizontal spindle and the corresponding pinion being mounted for rotation on a vertical spindle, and the spindle mounting the bevel or hypoid gear being axially movable to assist in mounting and demounting gears thereon and to bring gears mounted thereon into and out of mesh with corresponding pinions mounted on the other spindle, an automatic server comprising: a transfer device mounted for movement with respect to the machine for installing gear pairs at the work station and for removing gear pairs from the work station; the transfer device having two, spaced heads, each structured to grasp and let loose a gear pair, said two heads being so spaced that, at one disposition of the transfer device, one head is disposed to accept a gear pair to be installed at the work station and the other head is disposed adjacent the work station for removing a gear pair from the work station, and so that, at another disposition of the transfer device spaced from the first disposition, said other head is disposed to deposit a gear pair removed from the work station and said one head is located adjacent the work station for installing the gear pair accepted when the transfer device was last in the first disposition thereof.
 23. The automatic loader of claim 22 wherein each head of the transfer device is configured to grasp a pinion disposed with its longitudinal axis vertical and a bevel or hypoid gear with its longitudinal axis horizontal.
 24. The automatic server of claim 23 wherein when each head is disposed adjacent the work station, with the transfer device in one of said dispositions thereof, the head is aligned with the spindle for the bevel or hypoid gear so that spindle may be simply advanced and retracted axially to respectively mount and demount a bevel or hypoid gear respectively being brought by and removed by the head.
 25. For a machine for running gear pairs together in mesh at a work station for lapping or testing, each gear pair consisting of a bevel or hypoid gear and a corresponding pinion, the bevel or hypoid gear of the pair being mounted for rotation on a horizontal spindle and the corresponding pinion being mounted for rotation on a vertical spindle, and the spindle mounting the bevel or hypoid gear being axially movable to assist in mounting and demounting gears thereon and to bring gears mounted thereon into and out of mesh with corresponding pinions mounted on the other spindle, an automatic server comprising: a transfer device mounted for movement with respect to the machine for installing gear pairs at the work station and for removing gear pairs from the work station; the transfer device having at least one head structured to grasp and let loose a gear pair, said at least one head being configured so that when it is disposed adjacent the work station it is aligned with the spindle for the bevel or hypoid gear so that spindle may be simply advanced and retracted axially to respectively mount and demount a bevel or hypoid gear respectively being brought by and removed by the head. 